Fuel system and method for burning a liquid renewable fuel in engines and boilers

ABSTRACT

A process and apparatus is provided for burning liquid ammonia in an energy device such as a diesel engine, boiler or gas turbine. In particular, the process and apparatus include mixing a renewable fuel with a low flame speed and high ignition temperature, e.g., ammonia, with a combustible liquid fossil or bio-fuel and supplying the mixture into a closed fuel loop where part is efficiently burned in an engine combustion chamber, and part is used to cool the engine and returned by the loop for mixture with fresh incoming fuel mixture. The invention provides for the mixing and emulsifying in such a way that vapour lock is avoided. In the loop, the mixture is emulsified into a disperse distribution of fuel droplets such that upon injection of a portion into the combustion chamber, the renewable fuel in an emulsified droplet evaporates, mixes with the air and forms a small combustion cell surrounding the liquid fuel droplet. The fuel droplet burns and then serves as an ignition kernel for the gas mixture in the small combustion cell producing efficient and rapid combustion of the renewable fuel. The fuel loop allows the fuel system to automatically scale for engines varying in power output from  1  to  35,000  horsepower.

BACKGROUND OF THE INVENTION

The present invention broadly relates to fuel systems and, moreparticularly relates to a fuel system and method of forming anddispersing liquid ammonia/fuel oil emulsified droplets within acombustion volume of a conventional diesel engine, e.g., 5 hp to 35,000hp, boiler or gas turbine to produce efficient and rapid combustion ofthe ammonia/fuel oil mixture comprising the fuel emulsion.

At present, internal combustion engines, boilers and gas turbines, whichpower our cars, planes, trains and ships, and generate steam andelectricity at institutional, commercial facilities and utilities, relysubstantially on fossil fuels. The global supply of fossil fuels isknown to be finite and experts predict that they will run dry at sometime about the end of this century. It is obviously crucial to developrenewable energy sources to fuel the internal combustion engines,boilers and gas turbines to power our transportation and also thecommercial and industrial facilities and utilities.

While alternate forms of energy exist that can be adapted to supplyshort term needs, some of these are not environmentally friendly andtheir long term use may have an effect of poisoning our planet.Moreover, because our planet is comprised of air, water and earth, anyfuels derived there from to replace non-renewable fossil fuels should bereturnable to, or near their physical and chemical state aftercombustion. If we start with air and water to manufacture a renewablefuel, then the above objective can be achieved. The family of possiblefuels that can be derived or formed directly from air and water arethose containing hydrogen, nitrogen and oxygen. It is recognized thathydrogen, (H₂), is an excellent fuel, but it is known to be volatile anddangerous, and if mishandled, its use as a common fuel would put theaverage layperson in harm's way. In addition, as yet the technology forstoring, handling and distributing hydrogen is not fully developed.

It has nevertheless been proposed to set up a hydrogen economy wherehydrogen fuel cells would be substituted in the place of engines, tosupply power for transportation, commercial and industrial facilitiesand utilities. While this may be a long term objective, in alllikelihood, for example, it would take about twenty years to develop aviable hydrogen-fueled propulsion system and another twenty years tosubstitute/introduce it to replace existing fossil fuel driven engines.The projected costs for such a program are estimated to be very high,which would stress both government and corporate finances.

At this time ammonia, (NH₃), is an efficient hydrogen carrier, capableof implementation to render available hydrogen as a common fuel or fuelsupplement. Ammonia is readily available as an infinite renewable energysource, and can be introduced within a few years as a secondary fuelsource for existing combustion engines, thus eliminating both time delayand excessive costs associated with hydrogen. Technology for theutilization of gaseous ammonia as a fuel or fuel component in energydevices is already in progress, but combustion technology is not as yetavailable for the combustion of ammonia in high speed engines. That is,because of its high ignition temperature and slow flame speed, ammoniais a poor fuel for use in high-speed internal combustion engines.However, it is proposed to overcome these difficulties for internalcombustion engines by using liquid ammonia emulsified into anon-miscible liquid with low ignition temperature. These latter fuelcomponents can be identified as fossil or bio-fuels.

SUMMARY OF THE INVENTION

The present invention provides a means for overcoming the presentshortcomings of the combustion of ammonia.

It is an object of this invention to provide a novel ammonia-based fuelpreparation process that can be applied to conventional combustiondevices.

It is a further object of this invention to provide a means ofpreventing cavitation that can otherwise occur in fuel systemcomponents.

It is another object of this invention to provide a novel ammonia-basedfuel preparation process and system that can be incorporated intoconventional combustion devices with a minimum down time and expense.

It is another object of this invention to provide a novel ammonia-basedfuel preparation and system that overcomes combustion problems of fuelssuch as ammonia that display such characteristics as high ignitiontemperatures and low flame speeds.

It is another object of this invention to provide a fuel system andmethod that produces an ammonia/diesel fuel oil gaseous cellularstructure after injection into the combustion volume of the energydevice and said fuel cellular structure functions as a combustible unit.

It is a further object of this invention to provide a fuel system andmethod that produces a diverse dispersion of ignition kernels in anammonia/diesel oil fuel distribution within a combustion volume of theenergy device.

It is a further object of this invention to provide a fuel system andmethod that produces small gaseous cell sizes such that, upon ignitionof the diesel oil, the flame within the cell travels a small distance ina short interval of time thus obtaining complete chemical reactionquickly throughout the cell combustion volume.

It is still another objective of this invention to provide anammonia/diesel oil fuel system that operates a fuel mixing anddelivering control system that is scalable for variable sized enginesand boilers.

In one embodiment, the invention provides a fuel system and method forforming and delivering an ammonia/diesel oil emulsion to a conventionalcombustion chamber such that the ammonia is easily ignited and theensuing flame need only travel a short distance by confining an ignitionkernel within a small combustion cell.

A method of preparing a mixture of ammonia and fuel oil for use in aninternal combustion engine comprising first providing a supply ofammonia, liquid or vapor, at a predetermined pressure, temperature andflow rate to a metering-mixing module, second providing a supply of fueloil at a predetermined pressure, temperature and flow rate to themetering- mixing module, mixing a predetermined ratio of the supplies offuel oil the ammonia, liquid or vapor, in the metering-mixing module andsupplying the predetermined ratio of these fuels at a specifiedtemperature and pressure into a fuel control loop for use by theinternal combustion engine.

The step of supplying includes a) using a jet pump, first channellingthe predetermined ratio into an emulsifier sub-system to generate anemulsified fuel mixture flow, b) injecting a portion of the emulsifiedfuel mixture flow into a combustion chamber of the internal combustionengine to generate a disperse distribution of liquid fuel dropletstherein to facilitate the formation of small combustion cells and thusproduce efficient burning of both the ammonia and fuel oil components toprovide a desired power; c) where necessary a second channelling of theremaining portion of the emulsified fuel mixture flow through thecombustion engine head to cool the engine and d) recirculating theremaining portion exiting the combustion engine head to the jet pumpwhile regulating its temperature and pressure and combining it with theincoming predetermined ratio from the mixing-metering module in the stepof first channelling.

The method can include a step of implementing a heat exchange process onthe predetermined ratio prior to first channelling in the fuel controlloop. The step of first providing the supply of ammonia at thepredetermined temperature can include applying temperature control usingat least one heat exchanger and wherein the step of second providing thesupply of fuel oil at the predetermined temperature includes applyingtemperature control using at least one heat exchanger. The components ofthe fuel droplets in the disperse distribution generated in the step b)of injecting the portion of the emulsified fuel mixture flow arecharacterized by different evaporative characteristics. The differentevaporative characteristics cause the fuel droplet components toevaporate and shatter, thereby facilitating efficient combusting theammonia component. The step can include that one component is in aliquid state comprising a liquid kernel, i.e., core, and the othercomponent is in a gaseous state surrounding the liquid kernel to form acell. In this manner, the cell's liquid core functions as an ignitionkernel to the cell's gaseous volume surrounding the liquid core.

The method may include that the sub-steps of a) channelling andrecirculating the predetermined ratio and remaining portion exiting thecombustion engine head, respectively, allows for scaling thepredetermined ratio for a large range of internal combustion enginesizes, wherein the large range comprises combustion engines in sizesextending from 5 hp to 3500 hp. The present combustion engine is a 400HP Waukesha diesel engine. For this engine, the step d) of recirculatingthe remaining portion exiting the combustion engine head and combiningit with the first channelled predetermined ration includes facilitatesmixing fluid components characterized by different pressures to insuresmooth interacting flows that avoid or prevent slug flow. For thatmatter, a step of selecting of the liquid region of thermodynamicpressure-temperature space so that the temperate and pressure aremaintained in cooperating ranges in order that the liquid ammoniacomponent is not susceptible to vapor lock or cavitation.

In the method, the fuel droplet components with the differentevaporative characteristics are formed with a liquid particle atinjection into the combustion chamber of one of: a diesel engine, a gasturbine and a boiler. Alternatively, the fuel droplet components withthe different evaporative characteristics are formed with a solidparticle at injection into the combustion chamber of one of: a dieselengine, a gas turbine and a boiler. The step b) injecting the portion ofthe emulsified fuel mixture flow includes fuel droplet componentscharacterized with different ignition characteristics, and wherein oneof the fuel droplet components ignites the remaining fuel dropletcomponents in the combustion chamber. The step of mixing may include theuse of fuel additives in order to enhance the ignition and combustioncharacteristics of the fuel mixture. The fuel additives reduce the cyclepressure deviation thus producing smoother running engines and thusdecrease engine hunting.

The step of providing a supply of ammonia includes sensing a pressure ofammonia as it is pumped to the metering-mixing module, and based on thesensing, regulating the pumping to avoid vapour lock and cavitation. Thestep of first channelling includes sensing a pressure of thepredetermined ratio as it is pumped to the metering-mixing module, andbased on the sensing, regulating the pumping to avoid vapour lock andcavitation. The regulating includes utilizing a look-up table comprisingsaturation pressure verses temperature for the ammonia and fuel oilcomponents, and controlling the respective temperatures and pressuresbased thereon. Preferably, the step of providing further includes usingan ammonia pump motor that generates pumping power as a function ofmotor RPM, and controlling motor RPM as a function of a pressuredifference between the local pressure and a vapour pressure of ammoniabeing pumped, where the steps of first channelling and secondchannelling includes cooling the predetermined ratio and remainingportions respectively in a bypass controllable as function of detectedpressure and temperature

The invention also includes a fuel system for mixing a renewable fuelthat is normally slow burning with a fuel oil, emulsifying the mixtureand supplying the emulsified mixture to a combustion engine whileavoiding vapour lock and cavitation. The system comprises an ammoniasupply system for holding ammonia at its vapour pressure in order tosupply the ammonia in its liquid state, the ammonia system comprising afluid conduit connected to a heat exchanger and pump, a fuel oil supplysystem comprising a fuel oil reservoir, a fuel oil pump and a fuel oilpressure control device, a metering-mixing system in fluid communicationwith the ammonia and fuel oil supply systems, to mix the ammonia andfuel oil in a predetermined ratio, the metering mixing system comprisinga heat exchange means and pressure control means to maintain thepredetermined ratio at a temperature and pressure that avoids cavitationand vapour lock and a fuel emulsifier loop comprising a jet pump, a fuelmixture pump, a heat exchanger and a fuel emulsifier interconnected toenable a flow to a combustion engine, wherein the jet pump channels thepredetermined ratio into the fuel mixture pump and emulsifier sub-systemto generate an emulsified fuel mixture flow, and one portion of theemulsified fuel mixture flow is injected into a combustion chamber as adisperse distribution of liquid fuel droplets, a remaining portion ofthe emulsified fuel mixture flow through the combustion engine head tocool the engine and a remaining portion exiting the combustion enginehead is recirculated to the jet pump and combined with the incomingpredetermined ratio from the mixing-metering module.

The fuel system preferably further comprises a heat exchanger to preventcavitation in the fuel control loop, and a pressure and temperaturedetection and control means. The heat exchangers are connected to arefrigeration system. The fuel control loop includes a heat exchangerforming a bypass together with a three way solenoid valve to open andshut off the flow of ammonia and refrigerant in that bypass section. Thefuel control loop further includes a pressure sensor and motive devicesto control a local pressure based on detected ammonia saturationpressure determined as a function of temperature. A pressure sensordisposed at the entrance of the ammonia pump detects if pressure fallsbelow the saturation pressure of the ammonia, and responds by slowing amotor driving the pump, while operating the heat exchanger to lower theammonia temperature. For that matter, the invention includes acombustion engine comprising such a fuel system, and a combustion enginein which a fuel system with which the motor vehicle is initiallyconstructed is replaced with such a fuel system.

The invention includes a method of obtaining rapid combustion of amixture comprising a fuel characterized by a low ignition temperatureand high flame speed, and a volatile fuel comprising a high ignitiontemperature and low flame speed. The method comprises acts of producinga liquid fuel emulsion comprising the volatile and non-volatile fuels;compressing air in a compression stroke of an engine in order that theair temperature is greater than the ignition temperature of a componentof the fuel emulsion, injecting the liquid fuel emulsion into thecombustion volume in the form of a disperse distribution of droplets,wherein back heat transfer from the compressed air heats the fuelemulsion droplets thereby shattering the droplets and causing acomponent of the fuel to ignite and bum and thereby igniting theremaining volatile fuel-air mixture.

The method includes a step of maintaining the volatile fuel at apressure and temperature at which it is always in a liquid state untilthe droplets shatter. Preferably, the step of injecting produces adroplet size that is sufficiently small in order that the non-volatilegas flame progresses through the droplet gaseous cell in a time shortenough to completely combust. The method may include a step of addingfuel additives to enhance the ignition and combustion characteristics ofthe fuel mixture, wherein the step of adding fuel additives reduces acycle pressure deviation to minimize engine hunting.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Aspects of the invention will become apparent upon reading the followingdetailed description and upon reference to the accompanying drawings inwhich, like references, may indicate similar elements:

FIG. 1 is system level diagram depicting one embodiment of liquidammonia fuel system of the invention.

FIG. 2 is a system level diagram embodiment that can be substitutedwithin the liquid ammonia fuel system depicted in FIG. 1.

FIG. 3A is a plot on pressure-temperature plane of the

Clausius-Clapeyron locus, (C-C);

FIG. 3B a plot is shown of the thermodynamic process on thepressure-temperature plane, (C-C), occurring in a pressure regulatingvalve for a volatile substance corresponding to FIG. 2.

FIG. 3C a plot is shown of the thermodynamic process on thepressure-temperature plane, (C-C), occurring at the pump entrance for avolatile substance.

FIG. 4 is a system level diagram depicting a 3-part solenoid valve whichcan be utilized by the inventive system and method.

DETAILED DESCRIPTION OF THE INVENTION

The following is a detailed description of example embodiments of theinvention depicted in the accompanying drawings. The invention may takethe various forms of a fuel system, a method, an energy generatingdevice deploying the system and/or methods, which produce and deliver anammonia/fuel oil emulsion to a conventional combustion chamber such thatthe ammonia is easily ignited and the ensuing flame need only travel ashort distance by confining the ignition kernel within the cell.

The example embodiments are described in such detail as to clearlycommunicate the invention. However, the amount of detail offered is notintended to limit the anticipated variations of embodiments; on thecontrary, the intention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the presentinvention, as defined by the appended claims. The descriptions below aredesigned to make such embodiments obvious to a person of ordinary skillin the art.

For example, while the particular examples used and described herein aredirected to the use of ammonia (NH₃) as an exemplary sustainable fuelfor mixture (emulsification) with fuel oil, the invention is not limitedto use with ammonia. As known to those skilled in the art, ammonia (NH₃)displays a high ignition temperature and low flame speed, which as suchit is not compatible with modern high-speed combustion engines. Thecombustion model, fuel system and method described with the use ofammonia should be understood to be adaptable for beneficial applicationwith any renewable hydrogen-based fuel normally displaying low flamespeed and high ignition temperature, not just ammonia.

For that matter, the hydrogen-based fuel is meant to be emulsified witha renewable fuel oil. While the examples used and described herein aredirected to diesel oil specifically, which is non-renewable fossil fueloil, it should be understood that the description's diesel fueloil-based description is made for simplicity of explanation only. Theinvention is not meant to be limited to use with diesel oil or otherfossil-based fuel oils, but will be most valuable in an environmentalsense when used with fuel oils derived from plants and naturallyoccurring substances.

In a Venturi cavitation device a sequence of phases occurs for one ormore of the components of the fuel mixture, namely the phases changefrom liquid to vapor to liquid. In diesel engines the liquid fuelusually circulates through cooling passages in the cylinder head thusheating the fuel and possibly vaporizing part of it. A particularproblem occurs when one or more of the liquids are highly volatile inthat vapor lock occurs in the fuel lines or devices and renders theminoperable. We encounter a dichotomy; namely, we purposefully produce avapor/gas in a local part of the fuel emulsifier system, whether it isin the cavitating Venturi or the heated fuel lines. However, ultimatelywe require that the fuel be in the liquid state for injection into thediesel engine cylinder.

In the course of designing fuel systems for burners and engines, aparticular design was generated which has great merit. The very essenceof the design of the fuel system includes of a fluid loop with an inletto the loop and an exit from the loop to the engine or burner. Althoughthe design has been applied to both engines and burners, I shallrestrict this discussion and application to engines. The fuel loopoffers many advantages.

The fuel loop allows for fuel storage which circulates in the loop. Therange of engine sizes that can operate from a single loop is dependenton the amount of fuel withdrawn from the loop. Theoretically from alarge loop the engine sizes can range from 1 hp to 50,000 hp. This isfeasible but not practical. For example, the fuel emulsifier unitdesigned for the 400 hp Waukesha diesel engine can run engines fromabout 5 hp to 700 hp; and this is accomplished automatically without anymodification to the fuel system or engine.

The fuel loop contains the emulsifier, and this is placed adjacent tothe inlet of the diesel fuel manifold. The real time interval betweenthe fuel emulsion formation and fuel injection is short preventing fuel‘creaming’, i.e., separation.

In many diesel engines the fuel is used to cool parts of the engine. Ifthe fuel contains volatile components, then vapor lock can occur. It ismost probable that the fuel returning from the engine fuel manifold alsocontains vapors causing vapor lock. Two solutions become apparent tothis problem. The first solution is to increase the local fluid pressurein the loop segment up to its maximum value. This procedure alone maynot be sufficient to prevent vapor lock. The second solution is to coolthe fuel in that portion of the loop. The parametric combination ofthese two solutions can be observed by plotting the thermodynamic statesin the vicinity of the Clausius-Clapeyron locus in thermodynamicpressure-temperature space. The occurrence of vapor states then becomesobvious and can be prevented.

In our case liquid ammonia is the secondary component of the fuelmixture that is emulsified into the fossil fuel. The vapor pressure ofammonia varies widely with temperature. Of interest is the effect oflocal ambient temperature on the ammonia vapor pressure. Military andcommercial specifications may vary from −50 F to 110 F; and theconcomitant vapor pressures vary from 7.7 psia to 248 psia. The fuelloop described herein will operate at these extreme temperatures withoutmodification.

The emulsified fuel is immediately led into the diesel engine. A portionof the fuel is used by the engine to generate power. The excess fuelemulsion is used by this engine to cool the diesel head, thus weadditionally use a cooler to prevent vapor lock in the lines. It isrecognized that vapor lock can also be prevented by increasing the linepressure. The pressure in the line is maintained by a back pressureregulator valve.

Care must be taken for the selection of the liquid region ofthermodynamic space to develop processes for the liquid ammonia suchthat vapor lock is prevented in the ammonia fuel pump and othercomponents of the fuel system. If the pressure of the liquid ammonia isat its boiling point, then at the entrance to the ammonia pump, due tothe negative suction head, cavitation will occur. The fuel systemcomponent designs that accrue from the aforesaid criteria will suggestthe following designs.

Turning now to FIG. 1, a fuel system (1) for mixing a renewable fuel(e.g., ammonia) with a fuel oil (e.g., diesel), and emulsifying andsupplying the mixture to a engine combustion chamber (e.g., a dieselengine), constructed in accordance with the inventive principles inorder to avoid vapour lock and cavitation while effectively burning theemulsion will now be described. While the FIG. 1 system is intended foruse with a diesel engine, and is scalable for use with diesel engineswith varied power generating capacity, e.g., automobiles, trucks, ships,physical plants, etc., the fuel system is not limited to diesel engines.The FIG. 1 system (1) as shown comprises five sub-systems or functionalparts, namely: an ammonia supply system (10); a fuel oil supply system(20), a metering module or system (30), a fuel emulsifier loop (40) anda refrigeration sub-system (50).

Ammonia supply system (10) includes ammonia reservoir (11), which holdsammonia at its vapour pressure in order that it is maintained in itsliquid state. The ammonia is caused to flow in a fluid flow path fromthe ammonia reservoir (11) within a fluid conduit (9) to a heatexchanger (12) in order to cools the ammonia. The flow is controlled byan ammonia pump (13) in cooperation with a back pressure regulator valve(14; BPRV). The ammonia is pumped through a second heat exchanger (15),through ammonia flow meter (16) to a metering-mixing module (31), whichis part of mixing-metering module system, (30). Pressure gage (17) andshut off valve (18) are included for obvious reasons, and back flowpreventer (19) prevent any backflow of the liquid ammonia.

During the fuel system operation, the ammonia pump (13) enables the flowfrom the ammonia reservoir (11) in a liquid saturation state. The liquidammonia is sub-cooled by the heat exchanger (12). Heat exchanger (12) isattached to a refrigerator (50), as shown. The pressure of the liquidammonia is increased by pump (13), and limited by the BPRV (14). Theliquid ammonia is again cooled by heat exchanger (15). The availableammonia is at the liquid state as it enters the fuel line or conduit (9)of FIG. 1. As the liquid ammonia reaches pump (13), normally a negativesuction pressure develops producing cavitation, which withoutcompensation is likely to cause the liquid to boil and damage or destroythe pump.

The liquid ammonia flow rate is measured by the flow meter (16). Backflow preventer (19) maintains the flow lines and pump free fromcontamination. The pressure of the “in-line” liquid ammonia is detectedand communicated to an observer via pressure gage (17). The shut-offvalve, which may be either mechanically or solenoid operated, controlsstop/start the liquid ammonia flow to a first entry port E1 of themetering-mixing unit (31) in the metering system or module (30).

Before discussing the mixing-metering module or system (30), fuel oilsupply system (20) will be described in detail. That is, fuel oil supplysystem (20) comprises a standard fuel oil reservoir (21), for holdingand supplying fossil or non-fossil derived fuel oil. A conduit (19) incommunication with the fuel oil within the fuel oil reservoir (21)provides for a fuel oil flow through a filter (22) to a pump (24), theflow controlled by a BPRV (23). A pressure gage (25) and a back flowpreventer (26) are included to monitor and maintain the fuel-oil flowinto a second entry port E2 of the metering-mixing unit (31).

The metering-mixing unit (31) is part of a metering-mixing system (30),which receives liquid ammonia in first entry port El from ammonia supplysystem (10), and fuel oil in second entry port E2 from fuel oil supplysystem (20). The metering-mixing unit (31) meters and mixes the ammoniaand fuel oil, passing it along conduit (39) though a heat exchangers (32and (33), and into fuel emulsifier loop (40). Operation of themetering-mixing module is described in U.S. Pat. No. 4,468,127 to VitoAgosta, incorporated in whole by reference herein. The aforesaid U.S.Pat. No. 4,468,127, teaches how to design the module such that it variesthe fluid mixture ratio as a function of fluid volume flowing throughthe module.; i.e., to vary the mixture ratio as a function of engine orboiler load so that the combustion characteristics of the fuel mixturecan match those of the engine or boiler. The above said behaviour occursautomatically and is dependent on the thermo-fluid dynamics occurring inthe device. The heat exchanger (32) is used to cool the fuel mixture.

FIGS. 2 depicts an alternative embodiment of the ammonia supply system(10), operating in cooperation with fuel oil supply system (20). Thatis, FIG. 2 depicts an ammonia supply system (10′) and fuel oil system(20). No ammonia fuel pump is employed in the FIG. 2 ammonia supplysystem (10′). As such, fuel oil is injected into the ammonia streamwithin metering-mixing unit (31).

Operation of fuel emulsifier loop or system (40) is instrumental to thenovel and non-obvious operation of the ammonia fuel system (1), themethod and power consuming devices that operate in accordance with theinventive principles. Fuel emulsifier system (40) comprises a jet pump(41), a fuel mixture pump (46), a BPRV (45), a pressure gage (47), afuel emulsifier (48), all connected by a conduit (49) as a fluid flowpath to an entry port (51) of a engine manifold (52), e.g., diesel, of aconventional engine system. Excess fuel from the fuel manifold (52) iscarried out of exit port (53) via a conduit (49) back to the jet pump(41) through heat exchanger (44), the back pressure regulated by BPRV(43), and is monitored via pressure gage (42). Engine manifold (52)comprises fuel injectors and diesel head cooling passages, as known tothose skilled in the art.

The inventive system and method are unique in their ability to provide afor effectively mixing ammonia and fuel oil in order that it flow andburn in a conventional combusting chamber efficiently, and in a way thatscales readily for implementing relatively minimal fuel flow needs,e.g., for a van or passenger vehicle, to relatively large fuel flowneeds, e.g., for a large fuel-oil powered electrical generating plant orsystem. A significant feature inherent in the system's construction forconfiguration and cooperation with an engine manifold, in its operatingstate, allowing the capture and re-circulating of the fuel emulsion incontrolled fluid-flow loop that serves as well as a variable fuelemulsion storage means; this variable storage means, i.e., fuel loop, isnot attained by varying the volume of the flow lines in the system butby varying the fuel flow flux in the lines.

Operation of the fuel emulsifier loop or system (40) begins as the mixedfuel oil and ammonia entry into jet pump (41). The jet pump (41)essentially merges the fresh fuel charge with the re-circulated fuelsmoothly together without generating undesirable non-homogeneities suchas slug flow; and when properly designed, combines streams of differentpressures. The fuel mixture pump (46) together with the BPRV (45)prepares the fuel mixture for the operation of the fuel emulsifier (48).The operation of the fuel emulsifier is covered by U.S. Pat. No.3,937,445 to Vito Agosta, incorporated in whole by reference herein. Thediesel engine fuel manifold is not part of the inventive fuel system assuch, and it is shown to complete the flow passage circuit of the fuel.In this case, as occurs with the Waukesha diesel engine, there is anexcess of fuel which is employed to cool the diesel engine head andcirculates through fuel conduit (49).

The heat exchanger (44) follows to prevent cavitation of the fuel streamdue to the heat picked up in the diesel head. The BPRV (43) maintains apressure in line (49). It is recognized that both pressure andtemperature are parameters that can be modified to prevent vaporizationof any of the components of the fuel mixture or emulsion, i.e.,cavitation. Thus for the case where excess fuel, i.e., a fuel returnexists, and where it is used to cool parts of the diesel engine, bothpressure and temperature are varied in order to prevent cavitation. Thiscontrol is accomplished directly in cooperation with the heat exchanger(44) and the BPRV (43), and indirectly by the fuel pump sub-systemcomprising pump (45) and valve (46). The fuel conduit, (49), is made asshort as possible, and cavitation is prevented there and through the jetpump and line (49) by determining both pressure and temperature historyin lines (39) and (49), and fuel outlet temperature from heaterexchanger (32).

The refrigeration system (50) is employed to cool the fuel system (1) sothat cavitation is prevented. Together with the fuel pumps,refrigeration system (50) maintains the ammonia in the liquid state,both in and out of emulsion. That is, emulsifier (48; FIG. 1) operatesbased on the principle of evaporation at the “throat” of its Venturidesign and subsequent cavitation in the outlet diffuser. If the pressureis not recovered sufficiently downstream of the throat, then vapor lockwill persist in the fuel lines causing the diesel engine to “hunt.”,i.e., variation in engine speed. For proper operation, this unwantedvaporization must be overcome, and it is overcome by proper Venturidesign and operating conditions.

To eliminate the problem, it must be first understood. To do so, theClausius-Clapeyron locus for any volatile component of the fuel mixturemust be determined or calculated, and plotted in thermodynamicpressure-temperature space. In this case, the first task in solving theproblem of cavitation and vapor lock is to determine theClausius-Clapeyron locus for ammonia. The data can be deduced fromenthalpy-entropy charts and plotted on the pressure-temperature plane.The temperature is the abscissa and the pressure is the ordinate, asshown in FIGS. 3A, 3B and 3C.

Where data does not exist for this locus, it can be obtained in severalways. One way includes obtaining the critical point and the triple pointor the normal boiling point, and then using the thermodynamic law ofcorresponding states to develop the curve. Once the locus is developed,it is seen that an increase in pressure is represented by a verticalline, and a change in temperature is represented by a horizontal line(see FIG. 3A). While the real world is not ideal, the slope of theselines can be obtained by modifying the pressure or temperature as afunction of pump efficiency and heat transfer effectiveness, usingnormal thermo-fluid dynamic procedures.

As an example, referring to FIG. 1, if the heat exchanger, 12, were notplaced before the pump, 13, the incoming ammonia, being at itssaturation state and subject to the negative suction head would follow adecrease in pressure causing it to vaporize, destroying the pump. Byplacing a heat exchanger before the pump, the ammonia is cooled, drivingthe process to the left into the liquid region (see FIG. 3C). Thevertical distance between the end of that process and the C-C locus mustbe numerically greater than the suction head at the entrance to the pump(13).

The analysis of the emulsifier is more complicated in that the fluiddynamics must be combined with thermodynamics. Suffice it to say thatthe evaporation produced at the throat of the cavitating Venturi (atemulsifier (48)), must be suppressed by increasing the fuel mixturepressure in the Venturi exit. The increased pressure is maintained bythe BPRV (43) in the fuel emulsion loop. But the invention does not relyon high pressure alone in order to prevent the unwanted evaporation, butcontrols the pressure in combination with a cooling process concurrentlyand in cooperation with the pressure recovery process in the emulsifier(48) Venturi.

An actual liquid ammonia fuel system (1) was constructed according theFIGS. 1 and 3, operating in accordance with the fuel emulsion combustionmodel and used to fuel/power a 400 horsepower (hp) Waukesha dieselengine at 1800 rpm and 250 hp with 19% ammonia by mass. In this exampleammonia was used, but the operation applies equally well to any highlyvolatile substance.

Consider the circuits in FIG. 1 to be modified by adding a pressuresensor at the entrance to the ammonia fuel pump, (13), and anotherpressure sensor at the exit from the heat exchanger, (44). The purposeof these pressure sensors is to propose a control system to sense andprevent the vaporization of ammonia.

Let us place a thermometer in the room or site where the fuel system islocated. A thermodynamic table is set up relating the temperature to thesaturation pressure of the ammonia, values for which are provided in alook-up table that is accessible by a controller (60). Whenever thepressure at the aforesaid stations, (13) and/or (44), approaches thevaporization pressure of the ammonia, the following actions may occur.Consider first the fluid line (1), (39) and (49).

At the exit from the heat exchanger, (44), the pressure is increased bya valve to a value above the vapor pressure by activating the BPRV,(43). Several devices are already on the market to move an activatingarm attached to the BPRV, (43). The motion of the arm is madeproportional to the signal voltage, (read pressure difference betweenthe ammonia saturation pressure and a preset pressure difference abovethe saturation pressure. This is determined automatically by thecontroller (60) and adjusted in cooperation with the look-up tablevalues

A similar procedure can be followed for the case when the local pressureat the ammonia pump entrance, (13), falls below the saturation pressureof ammonia. A signal can be generated and sent by controller (60) to themotor speed control means to slow down the motor rpm thus decreasing thenegative suction pressure at the pump inlet. Alternately, an additionalsignal can be sent to open a solenoid valve, (90), to allow the ammoniapass through a sectional heat exchanger, (91), FIG. 4). If analysed on aC-C plot, it is seen that these coolers move the thermodynamic processesaway from the vapor state. It is also seen that vapor lock can be thusprevented by either slowing down the motor rpm, or extending the heattransfer from the ammonia.

Controller, (60) is connected to each of the subsystems (10), (20),(30), (40), and (50), FIG. 1. By thereby monitoring the pressure andtemperature of the ammonia, or indeed any of the volatile components ofa mixture, cavitation and vapour lock can be prevented. Alternatively,the heat exchangers and pumps are preset so that during operatingconditions, the maximum and minimum pressures and temperatures, andranges allowed are such that evaporation of the liquid ammonic in lines(9), (39) and (49) does not occur.

Although examples of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe following claims and their equivalents.

1-26. (canceled)
 27. A method of preparing a mixture of a liquidrenewable fuel and fuel oil for use in an internal combustion engine,comprising steps: providing a supply of renewable fuel to ametering-mixing module; providing a supply of fuel oil to themetering-mixing module; mixing a predetermined ratio of the supplies offuel oil and renewable fuel in the metering-mixing module; and supplyingthe predetermined ratio into a fuel control loop for use by the internalcombustion engine.
 28. The method as set forth in claim 27, wherein thestep of supplying including: using a pump, first channeling thepredetermined ratio into an emulsifier sub-system to generate anemulsified fuel mixture flow; injecting a portion of the emulsified fuelmixture flow into a combustion chamber of the internal combustion engineto generate a disperse distribution of liquid fuel droplets therein tofacilitate the formation of small combustion cells and thus produceefficient burning of both the renewable fuel and fuel oil components;and second channeling a remaining portion of the emulsified fuel mixtureflow to cool the engine.
 29. The method as set forth in claim 28,further comprising re-circulating the remaining portion exiting thecombustion engine to the pump while regulating its temperature andpressure and combining it with the incoming predetermined ratio from themixing-metering module in the step of first channeling.
 30. The methodas set forth in claim 27, wherein the step of providing the supply ofrenewable fuel to the metering-mixing module includes providing thesupply of renewable fuel at a predetermined pressure, temperature andflow rate to the metering-mixing module.
 31. The method as set forth inclaim 27, wherein the step of providing the supply of fuel oil to themetering-mixing module includes providing the supply of fuel oil at apredetermined pressure, temperature and flow rate to the metering-mixingmodule.
 32. The method as set forth in claim 27, wherein the step ofsupplying the predetermined ratio into the fuel control loop includessupplying the predetermined ratio at a specified temperature andpressure into the fuel control loop for use by the internal combustionengine.
 33. The method as set forth in claim 28, further comprising astep of implementing a heat exchange process on the predetermined ratioprior to first channeling in the fuel control loop.
 34. The method asset forth in claim 30, wherein the step of providing the supply ofrenewable fuel at the predetermined temperature includes applyingtemperature control using at least one heat exchanger.
 35. The method asset forth in claim 31, wherein the step of providing the supply of fueloil at the predetermined temperature includes applying temperaturecontrol using at least one heat exchanger.
 36. The method as set forthin claim 28, wherein, due to the generation of the emulsified fuelmixture flow, components of the fuel droplets in the dispersedistribution are characterized by different evaporative characteristics;wherein the different evaporative characteristics cause the fuel dropletcomponents to evaporate and shatter, thereby facilitating the formationwherein one component is in a liquid state comprising a liquid kerneland the other component is in a gaseous state surrounding the liquidkernel to form a combustion cell.
 37. The method as set forth in claim36, wherein the formation of the combustion cell includes forming acombustion cell having a liquid kernel which functions as an ignitionkernel.
 38. The method as set forth in claim 36, wherein the formationof the combustion cell includes forming a combustion cell having agaseous volume surrounding the liquid kernel which functions as anignition source.
 39. The method as set forth in claim 28, furthercomprising scaling the predetermined ratio of emulsified fuel for alarge range of internal combustion engine sizes.
 40. The method as setforth in claim 28, further comprising scaling the predetermined ratio ofemulsified fuel for a large range of internal combustion engines sizes,wherein the large range includes internal combustion engines in sizesextending from 1 hp to 35000 HP.
 41. The method as set forth in claim29, wherein the step of re-circulating the remaining portion exiting inthe combustion engine and combining it with the first channeledpredetermined ratio includes facilitating the mixing of fluid componentscharacterized by different pressures to insure smooth interacting flowsthat avoid or prevent slug flow.
 42. The method as set forth in claim27, further including a step of selecting of the liquid region ofthermodynamic pressure-temperature space so that temperature andpressure are maintained in cooperating ranges in order that therenewable fuel component is not susceptible to vapor lock or cavitation.43. The method as set forth in claim 36, wherein the fuel dropletcomponents with the different evaporative characteristics are formedwith a solid particle at injection into the combustion chamber.
 44. Themethod as set forth in claim 28, wherein the step of injecting theportion of the emulsified fuel mixture flow into the combustion chamberof the internal combustion engine to generate the disperse distributionof liquid fuel droplets therein includes generating liquid fuel dropletscharacterized with different ignition characteristics, and wherein oneof the fuel droplets ignites the remaining fuel droplets in thecombustion cells distributed in the combustion chamber.
 45. The methodas set forth in claim 27, wherein the step of providing a supply ofrenewable fuel includes sensing a pressure of the renewable fuel as itis pumped to the metering- mixing module, and based on the sensing,regulating the pumping to avoid vapour lock and cavitation.
 46. Themethod as set forth in claim 28, wherein the step of first channelingincludes sensing a pressure of the predetermined ratio as it is pumpedfrom the metering-mixing module, and based on the sensing, regulatingthe pumping to avoid vapour lock and cavitation.
 47. The method as setforth in claim 46, wherein the step of regulating includes utilizing acontroller and a look-up table, the look-up table comprising saturationpressure verses temperature values for the renewable fuel and fuel oilcomponents, and controlling the respective temperatures and pressuresbased thereon; wherein the step of providing further includes using apump motor that generates pumping power as a function of motor RPM, andcontrolling motor RPM as a function of a pressure difference between thelocal pressure and a vapor pressure of renewable fuel being pumped. 48.The method as set forth in claim 47, wherein the steps of firstchanneling and second channelling includes cooling the predeterminedratio and remaining portions respectively in a bypass controllable bythe controller as function of detected pressure and temperature.
 49. Themethod as set forth in claim 27, wherein the renewable fuel is liquidammonia.
 50. A fuel system for mixing a renewable fuel that is normallyslow burning at a high temperature with a fuel oil, emulsifying themixture and supplying the emulsified mixture to a combustion enginewhile avoiding vapour lock and cavitation, comprising: a renewable fuelsupply system for holding a renewal fuel at its vapor pressure in orderto supply the renewable fuel in its liquid state; a fuel oil supplysystem; a metering-mixing module in fluid communication with therenewable fuel and fuel oil supply systems for mixing the liquidrenewable fuel and fuel oil in a predetermined ratio; and a fuelemulsifier loop to enable flow of the renewable fuel-fuel oil mixture tothe combustion engine, wherein the predetermined ratio of renewablefuel-fuel oil mixture is channeled into an emulsifier sub-system forgenerating an emulsified fuel mixture flow, and one portion of theemulsified fuel mixture flow is injected into a combustion chamber as adisperse distribution of liquid fuel droplets, a remaining portion ofthe emulsified fuel mixture flows through a combustion engine to coolthe engine, and the remaining portion exiting the combustion engine isre-circulated and combined with the incoming predetermined ratio fromthe mixing-metering module.
 51. A motor vehicle including a combustionengine comprising a fuel system as set forth in claim 50, wherein theengine propels the motor vehicle.
 52. The fuel system as set forth inclaim 50, wherein the renewable fuel is liquid ammonia.
 53. A method ofpreparing a mixture of a renewable fuel and fuel oil for use in aboiler, comprising steps: first providing a supply of renewable fuel ata predetermined pressure, temperature and flow rate to a metering-mixingmodule; second providing a supply of fuel oil at a predeterminedpressure, temperature and flow rate to the metering-mixing module;mixing a predetermined ratio of the supplies of fuel oil and renewablefuel in the metering-mixing module; and supplying the predeterminedratio at a specified temperature and pressure into a fuel control loopfor use by the boiler.
 54. The method as set forth in claim 53, whereinthe step of supplying includes: using a pump, first channeling thepredetermined ratio into an emulsifier sub-system to generate anemulsified fuel mixture flow; injecting a portion of the emulsified fuelmixture flow into a combustion chamber of the boiler to generate adisperse distribution of liquid fuel droplets therein to facilitate theformation of small combustion cells and thus produce efficient burningof both the renewable fuel and fuel oil components to provide a desiredpower; second channeling a remaining portion of the emulsified fuelmixture flow to cool the boiler; and re-circulating the remainingportion to the pump while regulating its temperature and pressure andcombining it with the incoming predetermined ratio from themixing-metering module in the step of first channeling.
 55. The methodas set forth in claim 53, wherein the renewable fuel is liquid ammonia.